1. Field of the Invention
This invention relates to a direct-contact type cooling tank with upward refrigerant passage. In particular, the invention relates to a cooling tank for cooling water by bringing water in direct contact with hardly-water-soluble refrigerant having a larger specific gravity than that of water.
2. Description of the Prior Art
Research and development effort has been made on direct-contact type freezing cycle in which water is brought in direct contact with liquid of hardly-water-soluble refrigerant (including water insoluble refrigerant, to be referred to as "refrigerant" hereinafter) and the refrigerant is evaporated so as to cool water and to make ice. When such direct-contact type freezing cycle is applied to heat-storage type air cooling, considerable cost cut down is possible as compared with both conventional chillers and ice-making machines because refrigerant evaporators can be eliminated from chillers and freezing heat-exchangers can be eliminated from the ice-making machines.
The inventor disclosed his inventions relating to method and apparatus for storing heat in ice by using refrigerant jet in Japanese Patent Laying-open Publications No. 313657/1992 and No. 280842/1993. To facilitate the understanding of this invention, the method of the above Japanese Patent Laying-open Publication No. 313657/1992 will be briefly reviewed by referring to FIG. 7. The use of the cooling tank of this invention, however, is not limited to such method. With a water tank 1a of heat insulating construction, the pressure P.sub.t of the space 3 above water surface in the tank 1a is kept below the saturation pressure P.sub.0 of hardly-water-soluble refrigerant 2c at 0.degree. C. (P.sub.t .ltoreq.P.sub.0).
A mixer 4 mixes liquid-phase refrigerant 2c from a refrigerant liquid pipe 10 with water 2b from a cooling water return pipe 18 at a pressure P.sub.1 which is higher than the above saturation pressure P.sub.0 (P.sub.1 .gtoreq.P.sub.0). The liquid mixture of refrigerant 2c and water 2b is jetted through a nozzle 5 into the space 3 above the water surface.
Since water 2b is mixed with refrigerant 2c at the pressure P.sub.1 which is higher than the saturation pressure P.sub.0 of refrigerant 2c, water 2b does not freeze in the mixer 4, and the liquid mixture is jetted in liquid phase, so that refrigerant 2c evaporates in the space 3 above the water surface to produce ice 2a. As the liquid mixture is scattered in liquid phase, ice 2a can be dispersed over a wide area, and a heat exchange occurs very efficiently. Refrigerant which has evaporated in the space 3 in the tank 1a is extracted through a refrigerant gas outlet pipe 6 by a compressor 7, and after being liquefied, refrigerant 2c returns to the mixer 4. After being cooled by ice 2a and evaporation of refrigerant 2c, water 2b in the tank 1a is drawn through a cooling water outlet pipe 14 by a circulating pump 15, so as to pass through a heat exchanger 16 and return to the mixer 4. In the heat exchanger 16, cold water 2b provides cold heat to the piping 17 of an air conditioner 20. In the figure, a check valve 10a prevents water 2b from entering into the refrigerant liquid pipe 10 when the compressor 7 is at rest.
The inventor succeeded in using fluoropentanes as a refrigerant in the process of direct-contact type ice making, and disclosed such use in Japanese Patent Laying-open Publication No. 033046/1994. Heretofore, Freon (Trademark of Du Pont de Nemours & Co.) and hydrocarbons have been used as refrigerants for direct-contact type ice making. Freon has shortcoming in that it may cause depletion of ozone layer in stratosphere, and hydrocarbons such as pentane have shortcoming of being easily inflammable and require special fire-protective precautions. Perfluoropentane and other fluorinated pentanes such as fluorohydropentanes fulfill substantially all requirements for refrigerant of direct-contact type ice making, because they are free from the above shortcomings and have numerous advantageous points; namely, requiring no pressure-resisting tank for heat storage, being harmless, being incombustible, being free from reaction with water, and so on.